Duplex packaging material



y 9, 1967 w. E. ANDERSON 3,318,759

DUPLEX PACKAGING MATE-R I AL Original Filed Dec. 30, 1965 INVENTORWILLIAM E. ANDERSON Maw ATTORNEYS United States Patent Office 3,318,759Patented May 9, 1967 3,318,75? DUPLEX PACKAGING MATERIAL William E.Anderson, Bloomsbury, N..l'., assignor to Riegel Paper Corporation, NewYork, N.Y., a corporation of Delaware Continuation of abandonedapplication Ser. No. 334,447, Dec. 30, 1063. This application Dec. 7,1965, Ser. No.

7 Claims. (Cl. 161--235) ing material. These laminates areconventionally formed by the use of adhesives or like bonding agents andare characterized by their securely bonded plies. While theseconventional laminates have proved satisfactory for many applications,it has been found that in certain instances a loose-bonded duplex, i.e.,two plies of relatively stretchable and unstretchable material,positively and firmly bonded intermittently or at spaced surface areas,better utilizes the advantageous properties of each of the multipleplies. Such a loose-bonded packaging material is described in greaterdetail in the William E. Anderson et al. U.S. Patent No. 3,130,647,based on application Ser. No. 683,168, filed on Sept. 10, 1957, and,therefore, copending with the above-identified application Ser. No.334,447.

The so-called loose-bonded packaging material has enabled bagmanufacturers to produce a plural bag structure, i.e., a bag within abag, by methods and machinery normally and readily available for theproduction of conventional single walled bags. Thus, one of theimportant characteristics of the loose-bonded material is its elfectivehan'dleability as a single web of material, although, in fact, itcomprises two separate webs having little integrity.

The present invention represents an improvement in and a departure fromthe aforementioned patented invention. Specifically, the extremely goodand increased handleability of the new material and the increased easewith which it may be formed into a new and improved bag are importantaspects of the present invention. Moreover, While providing increasedhandleability, as compared to the loosebonded material, the new materialoffers substantial resistance to water vapor transmission.

In many packaging applications, a need has arisen for a material, suchas the new and improved packaging material, having the general handlingcharacteristics of the loose-bonded material in addition to certainproperties of stability and water vapor impermeability. Accordingly, itis an object of the present invention to provide a new and improvedpackaging material, which will optimally combine the properties of theplies of a laminate into a material having the above-described desirablecharacteristics. Another object of the invention is to provide such anoptimally combined laminate with the additional property of heatsealability. A more specific object of the invention is to provide apolyethyleneglassine laminate having great stretchability, greatstrength, water vapor impermeability, heat-scalability, and suflicientstability or temporary integrity to be readily formed into a completedpackage by conventional methods.

finished side.

In accordance with the principles of the invention, a new and improvedpackaging material is provided by weakly, i.e., temporarily orreleasably and non-readherably, bonding a pair of plies of relativelystretchable and unstretchable packaging material in a manner in whichthe plies are, in fact, bonded in overall face-to-face contact but withminimum bonding strengths in order that the laminate may retain asubstantially great degree of stretchabllity and a predetermined degreeof temporary integrity. The product of the invention is thuscharacterized as a weakbonded or as a temporary, readily releasably,non-readherably bonded laminate which has sutficient stability andtemporary integrity to be readily formed into a package while retainingunusually high degrees of both stretchability and strength due to therelatively great independence of it plies. The temporary bond betweenthe two plies of packaging material is of a predetermined minimumstrength less than the web strength of the plies in order that the bondwill fail, accommodating separation of the plies, before either of theplies fails or tears. Moreover, in accordance with the invention, thetemporary bonding agent provides water vapor impermeability to theweak-bonded" structure.

For a more complete understanding of the present invention, referenceshould be made to the following detailed description, taken inconjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of a new and improved heat-scalableweak-bonded" duplex sheet material embodying the principles of theinvention and partly broken away to show the components thereof;

FIG. 2 is a heat-sealed pouch fabricated from the material illustratedin FIG. 1; and

FIG. 3 is an enlarged cross-sectional view taken along line 33 of FIG.2.

With reference to FIG. 1, a new and improved weakbonded duplex packagingmaterial includes a relatively unstretchable base ply generallyindicated by the reference numeral 10, advantageously of a greaseresistant or greaseproof paper 11 such as glassine or the like. Inaccordance with the invention, the base paper 11 may include a coating12 of heat scalable thermoplastic material, for example, polyethylene,on its unprinted or un- As an important aspect of the invention, arelatively stretchable outer ply 13 of a thermoplastic film, such as afree film of polyethylene, is weak-bonded to the base ply 10 by atemporary or weak bonding layer 14. It has been found that for the bestresults the weak bond should be of such nature that the thermoplasticfilm 13 is separable from the base sheet 10 with a predetermined limitedpulling or separating force F exerted at a angle, of not less than about3 nor more than about 13 grams per inch of sheet width.

More specifically, a new and improved weak-bonded packaging material maybe made in accordance with the principles of the invention by supplyinga base sheet 11 of glassine having a basis weight on the order of 30pounds per ream (3,000 sq. ft.) and extruding a coating of polyethylenehaving a weight on the order of 7.5 pounds per ream thereon. A separateouter web 13, advantageously a free film of polyethylene or otherthermoplastic material, having a basis weight on the order of 30 .poundsper ream, is then temporarily and weakly bonded to the polyethylenecoated side of the base sheet 10 by a bonding agent layer 14 having aweight of about 4 pounds per ream and typically comprising a mixture of97 percent (by weight) parafiin wax and 3 percent butyl rubber, chewinggum grade, F.D.A. approved. As shown, the base ply 10 and the outer web13 are maintained in overall face-to-face contact by the bonding layer114.

While the above described bonding agent has given desired degrees ofcontrollably weak bonding and desired properties of water vaportransmission resistance in the combination described, the releasability,i.e., the degree of tightness of the bond between the free thermoplasticfilm and the coated glassine base may be controllably varied to suitparticular circumstances by using as little as zero percent, in somecases, or as much as 5 percent (by weight) butyl rubber in the wax-butylrubber bonding agent. Moreover, While a preferred temporary bondingagent employs butyl rubber as a tackifier, other tackifiers, such asElvaX (vinyl acetate-ethylene copolymers), Vistanex, wax soluble resins,microwaxes, and the like may also be suitable in lieu of or along withthe butyl rubber to controllably vary the degree of the weak bond.

A typical weak bonding agent is prepared from commercially availableproducts containing 30 percent butyl rubber and 70 percent paraffin wax,such as, for example, 5-85 Concentrate sold by Boler Petroleum Co.,Inc., Ardmore, Pa., or Polafin B30 CG sold by Moore & Munger, New York,N.Y., Which are combined with paraffin wax, for example 4312 w-axproduced by the Sun Oil Co., in the appropriate proportions to yield amixture having the desired (e.g., 97/3) wax-butyl ratio.

A duplex packaging material made in accordance with the abovespecifications will have an overall thickness of approximately 4.5 mils.

The new and improved duplex packaging material is adapted particularlyfor fabrication into packages in the nature of a pouch or bag, forexample (FIGS. 2 and 3), of the type having two opposing walls 16, 17,heat sealed at its peripheral edges 18 and adapted to package safely asensitive material M, such as a cake mix or the like, which must bemaintained free of changes in moisture content. As shown in FIG. 3, theheat seal 18 may be effected between the polyethylene films 13 and thepolyethylene coatings 12 by the application of heat and pressurethereto. In accordance with the invention, the heat sealing process willmelt and displace the weak-bonding agent 14, which has a lower meltingpoint than the thermoplastic material, so that the films and coatingsare fused by the heat and pressure. A significant function of thepolyethylene coating 12 is to promote proper heat sealing of the basepaper 11 with its associated film 13, after displacement of theweak-bonding agent. Thus, if the base sheet is formed of a materialwhich will accommodate proper heat sealing without use of the coating,or if the finished, weak-bonded laminate were to be used in applicationsnot requiring heat sealing, the coating 12 could be eliminated.

The new and improved packaging material and bags or the like fabricatedtherefrom will have great resistance to shocks and substantialresilience provided by the relatively stretchable thermoplastic film,while the relatively unstretchable paper base sheet provides substantialdefinition and static strength to the material. The realization of theseadvantageous properties is effected by maintaining the plies relativelyphysically independent, through the provision of a temporary or weakbond, so that in the completed package, the stretchable material may bereadily separated from and extended independently of the base sheet toabsorb shock. By way of comparison, in a conventional lamination ofrelatively stretchable and unstretchable materials, any substantialextension of the stretchable material will result in the rupture of therelatively unstretchable material.

It will be appreciated that the new and improved weak-bond duplexpackaging material possesses desirable strength and stretchabilityproperties similar to those found in loose-bonded materials according tothe beforementioned Anderson et al. US. Patent No. 3,130,647, inaddition to possessing particularly desirable physical and handlingcharacteristics and advantageous properties of water vapor transmissionresistance, stability, and heat scalability, all of which properties areespecially advantageous in the packaging of many materials. By utilizinga weak, temporary overall bond between the plies of the packagingmaterial, the strength properties of relatively unstretchable glassineand the stretchability properties of a polyethylene or similar film willbe realized to optimum advantage. These desirable properties of theindividual ply are not reduced or compromised (as is the case with aconventional laminate) due to the relatively great degree of physicalindependence retained by each ply of the new laminate through the use ofa weak bond in accordance with the principles of the invention.

It is to be understood that the weak or temporary, releasable,non-readherent bond contemplated in the application, in itstheoretically ideal or optimum form, should provide suflicient integrityfor the stretchable and unstretchable plies of the packaging material tobe handled as a single entity during bag-forming operation, andthereafter should provide no bond whatever. Thus a theoretically idealweak bond would provide absolute independence of the plies of thepackaging material after bag formation, leaving two absolutelyindependent bag walls. At present, a theoretically ideal weakly bondedpackaging material is not yet capable of manufacture by the art.However, it should be appreciated that the applicants new and improvedpackaging material represents the most practical, workable, andeflicient approximation of the theoretical ideal developed to date.Accordingly, the applicants inventive concept in its broadest formentails the provision of a composite packaging material havingrelatively stretchable and relatively unstretchable plies maintained inas maximally an independent relation as is feasibly possible whilehaving a uniform overall, bare minimum of adhesion which provides apredetermined degree of stability for handling the two independent pliesas one during a bag-forming operation.

It should be understood that the products and methods herein illustratedand described are intended to be representative only, as certaindepartures may be made therefrom within the clear teachings of theinvention. Accordingly, reference should be made to the followingappended claims in determining the full scope of the invention.

I claim.

1. A pre-assembled, flexible duplex pack-aging material weakly bondedwithout any heat sealing for the subsequent formation of bags or thelike having at least two separable walls, comprising (a) a first ply ofmaterial intended for the exterior of the bag having a property ofnon-stretchability similar to that of paper;

(b) a second ply of material intended for the interior of the bag havinga property of stretchability similar to that of a free thermoplasticfilm, whereby said second ply is substantially more stretchable thansaid first ply;

(c) said first and second plies being permanently heat sealable but notbeing heat sealed to each other;

(d) a releasable bonding agent substantially uniformly joining withminimum limited adhesion said two plies in substantially completeedge-to-edge contact by a temporary and weak bond of suflicient weaknessto accommodate a complete and permanent separation of said first andsecond plies;

(e) said weak bond being of a predetermined minimum strength less thanthe web strength of the first and second plies in order that the bondwill fail, accommodating separation of the plies, before either of thefirst and second plies fails or tears, and also being of less strengththan any subsequently formed heat seal bond at a seam or joint of thebag or the like;

(f) said temporary and weak bond thereby maintaining said two plies in asubstantially minimally adhered, temporarily integral relationshiphaving sufficient stability for handling;

(g) said bonding agent alone being the sole source of said limitedadhesion of said first and second plies and being applied as a unitarycomposition coating to at least one of the plies; and

(h) said bonding agent being non-tacky unless heated.

2. The duplex packaging material of claim 1, in which (a) said weakbonding agent is applied in overall faceto-face contact between saidplies and provides resistance to the transmission of water vapor throughsaid first ply.

3. The duplex packaging material of claim 1, in which (a) said first andsecond plies are separable by a predetermined limited separating forceexerted on one of said plies at substantially a 180 angle relative tothe other ply, said separating force being not less than about 3 normore than about 13 grams per inch of width of said plies.

4. The duplex packaging material of claim 1, in which (a) said first plyis a glassine paper material having an extruded polyethylene coatingthereon;

(b) said second ply is a polyethylene plastic film material; and

(c) said weak bonding agent includes paraffin wax,

(d) said extruded polyethylene coating thereby accommodating theformation of permanent heat sealed bag seams between said first andsecond plies.

5. The duplex packaging material of claim 4, in which (a) said weakbonding agent includes butyl rubber in percentages not in excess of 5percent by weight of said bonding agent.

6. The duplex packaging material of claim 4, in which (a) said glassinepaper material has a basis weight on the order of pounds per 3,000square feet;

(b) said polyethylene film ply has a weight on the order of 30 poundsper 3,000 square feet;

(0) said weak bonding agent has a weight on the order of 4 pounds per3,000 square feet; and

(d) said extruded polyethylene coating on said glassine has a weight onthe order of 7.5 pounds per 3,000 square feet.

7. A flexible packaging material in accordance with claim 1, in which(a) said weak bonding agent comprises parafiin wax and a tackifier notin excess of 5 percent by weight.

References Cited by the Examiner UNITED STATES PATENTS 2,415,387 2/1947Graebner et al. l6 l-235 X 2,422,725 6/1947 Gilfillon 161-12S X2,474,619 6/1949 Farrell et al 161-460 2,792,326 5/1957 Doyle et al.161-448 3,010,860 11/196-1 Eberl 16 1235 3,130,647 4/1964' Anderson etal. 156-201 X EARL M. BERGERT, Primary Examiner. CLIFTON B. COSBY,Examiner.

1. A PRE-ASSEMBLED, FLEXIBLE DUPLEX PACKAGING MATERIAL WEAKLY BONDEDWITHOUT ANY HEAT SEALING FOR THE SUBSEQUENT FORMATION OF BAGS OR THELIKE HAVING AT LEAST TWO SEPARABLE WALLS, COMPRISING (A) A FIRST PLY OFMATERIAL INTENDED FOR THE EXTERIOR OF THE BAG HAVING A PROPERTY OFNON-STRETCHABILITY SIMILAR TO THAT OF PAPER; (B) A SECOND PLY OFMATERIAL INTENDED FOR THE INTERIOR OF THE BAG HAVING A PROPERTY OFSTRETCHABILITY SIMILAR TO THAT OF A FREE THERMOPLASTIC FILM, WHEREBYSAID SECOND PLY IS SUBSTANTIALLY MORE STRETCHABLE THAN SAID FIRST PLY;(C) SAID FIRST AND SECOND PLIES BEING PERMANENTLY HEAT SEALABLE BUT NOTBEING HEAT SEALED TO EACH OTHER; (D) A RELEASABLE BONDING AGENTSUBSTANTIALLY UNIFORMLY JOINING WITH MINIMUM LIMITED ADHESION SAID TWOPLIES IN SUBSTANTIALLY COMPLETE EDGE-TO-EDGE CONTACT BY A TEMPORARY ANDWEAK BOND OF SUFFICIENT WEAKNESS TO ACCOMMODATE A COMPLETE AND PERMANENTSEPARATION OF SAID FIRST AND SECOND PLIES; (E) SAID WEAK BOND BEING OF APREDETERMINED MINIMUM STRENGTH LESS THAN THE WEB STRENGTH OF THE FIRSTAND SECOND PLIES IN ORDER THAT THE BOND WILL FAIL, ACCOMMODATINGSEPARATION OF THE PLIES, BEFORE EITHER OF THE FIRST AD SECOND PLIESFAILS OR TEARS, AND ALSO BEING OF LESS STRENGTH THAN ANY SUBSEQUENTLYFORMED HEAT SEAL BOND AT A SEAM OR JOINT OF THE BAG OR THE LIKE; (F)SAID TEMPORARY AND WEAK BOND THEREBY MAINTAINING SAID TWO PLIES IN ASUBSTANTIALLY MINIMALLY ADHERED, TEMPORARILY INTEGRAL RELAIONSHIP HAVINGSUFFICIENT STABILITY FOR HANDLING; (G) SAID BONDING AGENT ALONG BEINGTHE SOLE SOURCE OF SAID LIMITED ADHESION OF SAID FIRST AND SECOND PLIESAND BEING APPLIED AS A UNITARY COMPOSITION COATING TO AT LEAST ONE OFTHE PLIES; AND (H) SAID BONDING AGENT BEING NON-TACKY UNLESS HEATED.